02 Cabrio -- Chasing down ghosts and engine misfires

[taylormade]

Hi, I've got an 02 Cabio GLX 2.0L with 135k that's been giving me fits lately. Prior to now, we knew we had a coolant leak of some sort as we had to add water to the overflow bulb every three or four days.

While visiting us for the holidays, my old man tossed in half a bottle of Stop Leak, while I was out at work. Proud of himself, the coolant has stopped leaking... but now another, bigger, problem has surfaced and I don't know whether or not they're related. Here's the scoop:

Starts fine, idles fine when cold. As it reaches operating temperature (which it seems to do rather quickly, within say a mile or so), it starts misfiring. CEL reports Cylinder 3 misfire and pending codes are for 3 and 4 cylinders.

When I first hooked the computer up to the car, it had a TON of codes, but I'm not certain that they're all related, because I cleared them and all that's come back is the cylinder misfires.

Here's what was present BEFORE I cleared the codes:

Stored:
303 - Cylinder 3
304 - Cylinder 4
420 - Cat system
411 - Secondary Air Injection
300 - General Misfire

Pending:
116 - ECT
129 - Coolant Sensor or t-stat
139 - HO2S Circuit Slow Response (Bank 1 / Sensor 2)
341 - Camshaft sensor

I understand timing could be an issue based on the last line there but it only happens when it reaches operating temp. I'm going to replace the coolant sensor with a green top one and buy a distributor cap while I'm out as they're both cheap and need to be done anyway.

Anyone else got some suggestions to throw my way? Thanks!

[stealthpassat]

Never use stoppaleak in a can it does more damage than good.
Stare with cheap fixes first… Thermostat 10 bucks, cps like 30 bucks that good be what is going on with 139 check your downstream o2 sensor as well.

[taylormade]

Originally Posted by stealthpassat

Never use stoppaleak in a can it does more damage than good.
Stare with cheap fixes first… Thermostat 10 bucks, cps like 30 bucks that good be what is going on with 139 check your downstream o2 sensor as well.

Thanks, I should have added the following:

It's not EVERY time that it does this either... just to add to the fun

It's more than not, but every once in a while when I'm trying to replicate it, it will run just fine.

I just found a loose cable (appears to be a ground) from the valve cover that runs to the ignition coil and tightened it down snug. Took around the block a few times, no problems. I'm hoping that somehow that was the problem but I don't think I'll get off that easy as nothing with this car has been easy.

After tightening the ground for the ignition coil, I drove the car, without problem for about 5 minutes and let it cool off a bit. I let it sit for about an hour and just drove it 20 miles with no problems with a 20 minute stop in between.

When I got home, I thought I'd test my theory that the ground was the problem. So I loosened the nut and let the bracket swing freely, driving another 2 miles... without problem...

I'm going to try again in just a few minutes, it should be cold again, and I'll give it another whirl. I have other issues to work out, like oil that's dripping ever so slowly onto the exhaust manifold and a vacuum hose that has been disco'd and I have no clue where it goes... but for now, this is the problem that REALLY needs solving as it's affecting my daughter's ability to go to work and school.

I can try the ECT and thermo tomorrow, thanks for the advice!

[taylormade]

Oh, also, I cleared the codes and the only one that came back was the 411 for secondary air injection... probably has to do with the hose I found disconnected.

[taylormade]

Update:

I got up this morning after letting it sit overnight expecting to have the car go into fits again, and it did not. It's driving very nicely. I drove about 10 miles and it's been running great.

Question:

this used car didn't come with a manual... what's the recommended octane gas?

She's been putting in 87 (lowest around here in Tampa), but I put 89/93 in my truck and it runs so much better than when I use the cheap stuff. I know certain engines don't like higher octane fuel... is this one of them, or should I try a tank or three of 93?

[Shameless]

Should say it on the damn gasdoor.

Higher octane fuel will never be an issue unless you're running some shabby plugs/coilpack/ignition in general and the ecu can't compensate, but this isn't the issue. Our motors do run on the hotside but you should be fine with filling your 2.0 with 86 octane. It's an eco car.